Prosecutors also amended five other counts that Holmes, 24, already faced. Details about the new charges were not made public.

Holmes is accused of donning body armor and killing 12 people and injuring 58 after opening fire in a movie theater July 20 during the crowded midnight premiere of The Dark Knight Rises. Holmes already faces multiple murder and attempted-murder charges.

The former neuroscience graduate student sat quietly during Thursday's 75-minute court hearing. He didn't react when defense attorney Dan King said there's so much preliminary investigation remaining in the case that "we cannot begin to examine the nature and depth of Mr. Holmes' mental illness."

Also in court on Thursday, defense attorneys and prosecutors objected to continuing efforts by the news media, on behalf of the public, to learn more details about the case against Holmes.

At one point, reporters were accused of treating victims as not much more than "cannon fodder."

Said King: "Many of the witnesses are in hiding because of the conduct of the media in this case."

Holmes is scheduled back in court for an Oct. 25 hearing aimed at answering whether police investigators improperly leaked information about the case to the media.

The judge set a Jan. 7 date for a preliminary hearing in the case. The judge is likely to decide whether prosecutors have enough evidence to proceed with their case against Holmes.

That hearing also will give the public its first solid look at the evidence against Holmes, and provide a glimpse of his defense strategy. Holmes is widely expected to use a mental illness defense.